Widespread bacterial utilization of guanidine as nitrogen source

Abstract

Although guanidine is widely used in the manufacturing of plastics, as reactant in certain explosives and propellants and as a chaotropic reagent in biochemistry, a prominent role in nature has not been identified to date. The lack of knowledge about the physiological role and source of free guanidine in biological systems is in bright contrast to the widespread occurrence of guanidine riboswitches.

Canavanine utilization via homoserine and hydroxyguanidine by a PLP-dependent γ-lyase in Pseudomonadaceae and Rhizobiales

“…55,56 This explains why the majority of hydroxyguanidine is exported and not used by the bacterium for nitrogen assimilation as we have demonstrated recently for guanidine. 24 The homology search of the canavanine-g-lyase revealed that the enzyme is also found in Rhizobiales. We confirmed that the CangL homolog of R. leguminosarum is indeed degrading canavanine.…”

“…55,56 This explains why the majority of hydroxyguanidine is exported and not used by the bacterium for nitrogen assimilation as we have demonstrated recently for guanidine. 24…”

Characterization of Structure and Dynamics of the Guanidine‐II Riboswitch from Escherichia coli by NMR Spectroscopy and Small‐Angle X‐ray Scattering (SAXS)

“…These guanidine riboswitches (Gdn) sense Gdm + with high sensitivity and specificity [17] . Derived from the genomic location of the Gdm + ‐sensing riboswitches, Gdm + has then been proposed to play an important role in the detoxification of cells via its carboxylation [13] but also to serve as a source of nitrogen [18] …”

“…[17] Derived from the genomic location of the Gdm + -sensing riboswitches, Gdm + has then been proposed to play an important role in the detoxification of cells via its carboxylation [13] but also to serve as a source of nitrogen. [18] To date, four different classes of Gdm + -sensing riboswitches have been discovered termed guanidine-I to guanidine-IV. [15,18,19] Many of these Gdm + -sensing riboswitches are biologically well characterized and structural models of isolated hairpins were reported for all the four riboswitch classes including Gdn-II from Escherichia coli (PDB: 5NDI), from Gloeobacter violaceus (5NOM and 5NDH) and from Pseudomonas aeruginosa (5VJ9).…”

“…[18] To date, four different classes of Gdm + -sensing riboswitches have been discovered termed guanidine-I to guanidine-IV. [15,18,19] Many of these Gdm + -sensing riboswitches are biologically well characterized and structural models of isolated hairpins were reported for all the four riboswitch classes including Gdn-II from Escherichia coli (PDB: 5NDI), from Gloeobacter violaceus (5NOM and 5NDH) and from Pseudomonas aeruginosa (5VJ9). [14,20] The structures reveal striking similarities of ligand binding pockets between these different riboswitches.…”